Raney nickel-aluminium alloy

Phenol in 10% sodium deuteroxide in deuterium oxide upon treatment with Raney nickel-aluminium alloy and heating at100 C for 3 hours afforded a pentedeurated product in 86% yield (ref.63). 

The most important example of this category is Raney nickel, which is extensively used in hydrogenation reactions in fine chemistry. The catalyst has been named after Murray Raney who invented this catalyst in 1924. It is prepared by the reaction of a powdered nickel-aluminium alloy with aqueous sodium hydroxide to selectively remove a large fraction of the aluminium component (.see Figure 3.12). The product consists of porous nickel with a high... 

Raney nickel (often abbreviated to RaNi) is a finely divided form of nickel made from a nickel-aluminium alloy. The aluminium is dissolved away using concentrated aqueous sodium hydroxide, leaving the nickel as a fine powder. The process liberates H2 (check this for yourself— on paper ), and some of this hydrogen remains adsorbed on to the nickel catalyst. This means that some hydrogenations, particularly those of C-S bonds, which you will come across later in... 

Raney Nickel (nickel-aluminium alloy) is an effective catalyst for the conversion of thioketals to alkanes. Ultimately, a ketone is converted to the alkane with this mild method through a thioketal. Review Pettit, G. R. van Tamelen, E. E. Org. React. 1962,12, 356-529. 

Raney nickel A spongy form of nickel made by the action of sodium hydroxide on a nickel-aluminium alloy. The sodium hydroxide dissolves the aluminium leaving a highly active form of nickel with a large surface area. The material is a black pyrophoric powder saturated with hydrogen, it is an extremely efficient catalyst, especially for hy-... 

A recent modification in the use of Raney nickel may greatly enhance its utility. Industrial use of the standard procedure has been limited by the necessity to use such large quantities of the very expensive Raney nickel. It now appears that the use of the nickel-aluminium alloy itself in formic acid leads to very efficient desulphurizations with Ni/S ratios of only 0 2. High proportions of the aluminium seem to give the best results, apparently because of the ability of the aluminium to regenerate the active nickel catalyst. Similar results were obtained using nickel or cobalt salts in the presence of auxiliary metals such as aluminium or iron. 

The Raney nickel catalyst is prepared through the action of aqueous alkali on a nickel-aluminium alloy. The conditions employed allow the preparation of the catalyst with a specific activity. Furthermore, the catalyst may be deactivated by refluxing with hydrogen acceptors, by degassing or by ageing. For details the reader is referred to the reviews mentioned above. 

Raney nickel is a finely powdered nickel-aluminium alloy that contains hydrogen absorbed onto the surface... 

Raney nickel is a useful catalyst for hydrogenations at mild conditions. It is, however, sensitive to poisoning and not very stable at high temperatures. Another disadvantage is that regeneration is not always possible in many cases the catalyst must be melted with aluminium until the right Al-Ni alloy is formed. Then the preparation procedure has to be repeated again. Moreover, the preparation procedure is not very reproducible. 

Aluminium-nickel alloys (Raney nickel alloys)... 

Heating moist Raney nickel alloy containing 20% aluminium in an autoclave under hydrogen caused the aluminium and water to interact explosively, generating 1 k bar pressure of hydrogen. 

A Raney nickel surface is also suitable for electrocatalytic hydrogenation [205]. This surface is prepared by electrodepositing nickel from a solution containing suspended Raney nickel alloy (Ni 50% A1 50%). Some alloy particles stick to the surface, which is then activated by leaching the aluminium using hot aqueous sodium hydroxide. Cyclohexanone, acetophenone and benzil have been converted to the corresponding alcohol and there is no stereoselectivity for the formation of hydrobenzoin from benzil. 

The introduction by Raney (1927) of a new form of catalyst (the Raney nickel catalyst) with enhanced activity for hydrogenation at low pressures and temperatures in comparison with the usual form of nickel catalyst as employed by Sabatier and Senderens opened up a new field of controlled catalytic hydrogenation. A special alloy, prepared essentially by the fusion of approximately equal parts of aluminium and nickel at 1200-1500 °C, is treated with alkali which dissolves the aluminium and leaves the nickel as a finely-divided black suspension. The catalyst is thoroughly washed to free it from alkali, is stored under absolute ethanol in an air-free container and is measured in the... 

Raney cobalt alloy, see Aluminium—cobalt alloy, 0049 Raney nickel alloys, see Aluminium—nickel alloys, 0055 Resorcinol diacetate, see 1,3-Diacetoxybenzene, 3285 Resorcinol, see 1,3-Benzenediol, 2325 Rhenium hexafluoride, 4367 Rhenium hexamethoxide, 2599 Rhenium nitride tetrafluoride, 4338 Rhenium, 4884... 

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